The present invention relates to a rung or upright for a cable ladder, to a cable ladder and to a process for assembling same.
As shown in accompanying FIG. 5, it is known to make a cable ladder for supporting electrical leads, in a vertical or horizontal configuration, by assembling lateral uprights 101 and tie-bars or rungs 102, these rungs extending principally in a direction substantially perpendicular to that of the uprights. These uprights and rungs are assembled together by means of screws or rivets 103 which allow immobilization of the rungs and the screws in a direction perpendicular to the plane of FIG. 5. Oblong perforations 104 are usually provided in the uprights 101 and oblong perforations 105 in the rungs 102, these perforations allowing, on the one hand, passage of the screws 103 and, on the other hand, passage of the ties for attaching the leads (not shown in FIG. 5). A comparison of the solid-line configuration and that in dashed and dotted lines in FIG. 5 shows that the rungs 102 can pivot with respect to the uprights 101 parallel to the plane of FIG. 5, with the result that the ladder can be deformed, which is both unaesthetic and may lead to parasitic movements of the ladder. In addition, in the known configuration, the screws or rivets 103 are subjected to an intense shearing effort which may lead to rupture thereof.
It is a particular object of the present invention to overcome these drawbacks by proposing a rung structure which allows a particularly solid assembly with known uprights, without risk of deformation of the ladder produced and with a considerable reduction of the shearing effort undergone by an attaching member.
To that end, the invention relates to a rung for a cable ladder comprising at least one orifice for passage of a member for attachment to an upright, characterized in that it also comprises two elements in relief arranged on either side of this orifice and adapted to be engaged in an oblong perforation in the upright in which the attachment member is received.
Thanks to the invention, the elements in relief make it possible to centre the orifice for passage provided in the rung with respect to the oblong perforation provided in the upright and thus to create a plurality of points of contact between the rung and the edge of the oblong perforation, with the result that pivoting of the bar about the axis of the attachment member may be avoided. The elements in relief may bear against the edges of the oblong perforation, with the result that they absorb most of the shearing efforts to which the join between the rung and the upright is subjected. The attachment member, which may be a screw or a rivet, is accordingly less subjected to shear.
The invention is also applicable if the above-described structure is inverted, in which case it relates to an upright for cable ladder which comprises at least one orifice for passage of a member for attachment to a rung and two elements in relief disposed on either side of this orifice and adapted to be engaged in an oblong perforation in the rungs in which the attachment member is received.
As previously, the elements in relief participate in the centering and take-up of effort between the rung and the upright.
Whatever the variant considered, the elements in relief are advantageously formed by bosses obtained by localized deformation of a web of the rung or the upright. These elements in relief are thus particularly economical, while being able to withstand considerable efforts.
According to an advantageous aspect of the invention, these elements in relief present a geometry adapted each to abut against the edge of the oblong perforation, the cooperation of shapes between these elements in relief and this edge ensuring a relative immobilization of the rung and the upright around the attachment member.
The elements in relief can also be provided to be deformable, by tightening the attachment member, so that they come into close abutment against the edge of the oblong perforation. In this way, the effect of positioning and tightening the attachment member is to crush these elements in relief to the point of being blocked against the edge of the oblong perforation.
According to other advantageous aspects of the invention, the elements in relief can be provided to be substantially conical or in the form of a spherical cap, with a maximum diameter substantially equal to the smallest dimension of the oblong perforation.
In addition, in this case of a rung, an orifice for passage of an attachment ember and two elements in relief are provided near each of the ends of the rung.
The invention also relates to a cable ladder comprising at least one lateral upright and a rung as described hereinabove. Such a ladder is more rigid than the prior art ladders, while its cost price is not substantially modified with respect thereto.
Finally, the invention relates to a process for assembling such a ladder as described hereinabove, in which a rung and a lateral upright are connected by inserting an attachment member in an orifice in this rung and a perforation in this upright. This process consists in positioning the orifice and the perforation with respect to each other, introducing into this perforation elements in relief disposed on either side of this orifice.